This application claims priority of DE 198 51 744.0, filed Nov. 10, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a transport and/or positioning system, particularly for the workpiece transfer, particularly for transporting sheet metal pieces in the case of transfer presses.
Machining systems having several machining stations arranged in series require a workpiece transport from one working station to another. For this purpose, transfer systems are used which receive the corresponding workpiece, such as a sheet metal piece, in a machining station; guide it out of the latter; place it in the next machining station; and release the workpiece there, in order to remain in a parked position spaced away from the machining station during the machining of the workpiece.
Particularly in the case of large-piece presses, in which large-surface body parts of motor vehicles, in individual cases, entire side pieces of vehicle bodies, are machined, the pieces are several meters wide. Correspondingly, the distance between individual machining stations is relatively large. In this situation, the sheet metal pieces have a considerable weight. In order to permit a high stroke rate of the transfer press, these pieces must be transported relatively rapidly. That is, they must be accelerated and braked again from one working station to another in a relatively speedy manner, in which the transfer system must generate the driving power at the workpiece required for this purpose and must simultaneously ensure a high positioning precision.
Transfer systems, which are to carry out the workpiece transport, for example, between press stations, are also subjected to relatively narrow constructive marginal conditions. It is, for example, desirable for the space laterally next to the press sliding tables to remain free so that the sliding tables can be moved unhindered by the transfer system laterally out of the transfer press.
An object of the present invention is, therefore, to provide a transport and/or positioning system which permits the bridging of relatively long transport paths in a short time and a precise positioning of the transported pieces.
This object has been achieved by a transport and/or positioning system, a drive device which has at least one lever mechanism with an output for driving and positioning a carrier device, the lever mechanism including a swivel arm whose one end forms the output and is connected with the carrier device and which is connected at two mutually spaced connection points with a bearing and with a drive, the distance between the bearing point and the driving point being smaller than the distance between the output and the bearing point.
The transport and/or positioning system has a lever mechanism with a swivel arm which carries a carrier device on one end. The carrier device can be engaged with the workpiece or can receive the workpiece in a different manner. The swivel arm is situated in the power transmission path which extends from a drive source to the carrier device. In this case, the swivel arms carries out a step-up. It is guided and driven at two points spaced away from the carrier device, the distance between these two points being smaller than the distance of the carrier device from the swivelling axis of the lever. This therefore results in a lever transmission. This lever transmission has the result that the carrier device carries out a faster and more extensive movement than drive devices applied to the swivel arm.
These drive devices may include guides, such as linear guides, slide blocks and similar devices. Because these reach a lower maximal speed and cover shorter paths than the carrier device, their mass is not as important for the dynamics of the drive as the mass of the carrier device. They may be designed such that they result in a precise guidance. A high positioning precision can therefore be reached at the carrier device. As a result of the lever transmission at the swivel arm, it therefore becomes possible to rapidly travel long transport paths with a good precision.
In a currently preferred embodiment, two mutually mirror-symmetrical drive devices have swivel arms connected with one another by means of a traverse which forms the carrier device. The traverse may, for example, be provided with suction spiders or other devices for temporarily carrying workpieces. The cross traverse is guided by the two swivel arms preferably on a loop-shaped path which forms the transfer curve and which extends, for example, in a vertical plane. As a result, with respect to the function, a two-axis transfer is provided in the case of which the cross traverse is moved vertically and horizontally. The path or the transfer curve is not fixedly defined but is preferably selectable or adjustable in that drives pertaining to the drive unit are correspondingly controlled. This is preferably carried out by a programmable control device. If the drive devices applied to the two ends of the traverse are controlled in a different manner, the traverse can also carry out swivelling movements about a vertical axis or an axis situated longitudinally with respect to the transport direction.
The carrier device, such as the traverse, can be provided with a device in order to hold the traverse non-rotated or rotate (tilt) it in a targeted manner when travelling through the transfer curve. This can take place by way of separate drives carried by the swivel arms as well as by way of power transmitting devices, ranging from parallelogram linkages or pulling device transmissions to drives arranged in different manners.
The swivel arm can be swivelled about an axis of rotation which is not stationarily arranged but can be adjusted along a defined path. The swivelling axis can be defined, for example, by a suitable bearing on a slide block, the slide block being disposed on a guide. The slide block guide can be oriented vertically, as required, also horizontally or otherwise, and can be straight or bent. Alternatively, the bearing of the swivel arm defining the axis of rotation may also be guided differently, for example, by way of a rocker, a parallelogram or similar devices.
In a preferred embodiment, the swivel arm is vertically oriented in the center position and, for implementing a transport step, swivels out to both sides. In the center position, which may be considered the parking position, the sides of the sliding tables of the adjacent machining stations are free and therefore also accessible. This is advantageous for the exchange of tools. In addition, it is possible to arrange the drive device above the tables. The space below and between the tables therefore remains free for waste chutes and scrap metal conveyer belts.
The drive device can be disposed on the press stands, which permits an extremely space-saving construction and avoids problems of a separating point between the press stands and the tables.
The lever mechanism, which includes the swivel arm, can have different constructions. It may, for example, have a guide rod which is connected at a connection point in an articulated manner with the swivel arm and which is connected with a rotary drive. If the rotary drive is held, for example, on a slide block displaceably disposed on a guide, which slide block itself is connected with a stationary drive device, a targeted controlling of the slide block drive and of the rotary drive allows a desired curve of the carrier device to be driven.
In a preferred embodiment, the slide block is disposed in a vertical guide. The guide rod is applied approximately in the center to the swivel arm, whose end away from the carrier device is, in turn, swivellably disposed on a slide block whose linear guide is aligned in parallel to the former guide. In this embodiment, very clear controlling and driving conditions are obtained, particularly if the length of the guide rod corresponds to half the length of the swivel arm, which is defined by the distance of the devices or the tilting axis from the swivelling axis of the swivel arm, and if, in addition, the guide rod is applied in the center to the swivel arm. In this case, a control of the slide block drive causes only a vertical adjustment of the carrier device, and a control of the swivel drive causes only a linear adjustment of the carrier device in the transport direction.
Alternatively, the swivel arm can be driven by two mutually interacting guide rods which are arranged at an acute angle with respect to one another and which are fastened on the swivel arm by an articulation which defines, for both guide rods, a coinciding or joint axis of articulation. On their other ends, the guide rods are preferably suspended in an articulated manner on slide blocks of a linear guide which are provided with linear drives. The guides may be provided vertically at the press stands and have a vertical guiding device. A compact construction is obtained, in which the transport movement of the carrier device is achieved without the requirement of providing force transmission devices extending in the transport direction. Because of the step-up by the swivel arm, the linear strokes to be travelled by the slide blocks are relatively short, so that a compact space-saving construction is achieved.
As required, the guide rods and/or swivel arms can be constructed in a longitudinally adjustable manner. This can provide additional degrees of freedom when guiding the carrier device.
The drive device is preferably connected with a force generating device which, by way of the lever mechanism of the drive device, guides a compensation force to the carrier device which at least approximately compensates the weight of the carrier device and of the connected lever mechanism. The force generating device can be applied by rotatingly driven guide rods to its slide blocks. In addition, the rotary drive can be force-compensated. For this purpose, the guide rod can be acted upon, at a point between its swivelling axis and the axis of articulation, by means of a more or less constant force which is directed essentially vertically upwards or, on the other side of the swivelling axis, is directed downward. This may take place by pneumatic cylinders.
In the embodiment with two guide rods arranged at an acute angle with respect to one another, for operating the swivel arm, the weight compensation can take place by way of a third guide rod which is applied to the swivel arm by an essentially identical hinge axis and extends to another vertical slide block. This vertical slide block is connected by a linkage with a force generator, such as a pneumatic cylinder, which guides a largely constant, vertically upward-directed force onto the slide block.